/*
 * @Author: NgSiuKei
 * @Date: 2021-06-19 16:12:34
 * @LastEditTime: 2021-06-21 19:51:23
 * @LastEditors: NgSiuKei
 * @Description: 
 * @FilePath: /Linux高性能服务器编程/并发Web服务器/http_conn.cpp
 * 我是一个人类。你不是一个孤岛。
 */

#include"http_conn.h"

//定义HTTP响应的一些状态信息
const char * ok_200_title = "OK";
const char * error_400_title = "Bad Request";
const char * error_400_form = "Your request has bad syntax or is inherently impossible to satisfy.\n";
const char * error_403_title = "Forbidden";
const char * error_403_form = "You do not have permission to get file from this server.\n";
const char * error_404_title = "Not Found";
const char * error_404_form = "The requested file was not fount on this server.\n";
const char * error_500_title = "INternal Error";
const char * error_500_form = "There was an unusual problem serving the requested file.\n";

const char * doc_root = "/var/www/html/index.html";//网站的根目录

int setnonblocking(int fd)
{
    int old_option = fcntl(fd, F_GETFL);
    int new_option = old_option | O_NONBLOCK;
    fcntl(fd, F_SETFL, new_option);
    return old_option;
}

void addfd(int epollfd, int fd, bool one_shot)
{
    epoll_event event;
    event.data.fd = fd;
    event.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
    if(one_shot == true)
    {
        event.events != EPOLLONESHOT;
    }
    epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
    setnonblocking(fd);
}

void removefd(int epollfd, int fd)
{
    epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, 0);
    close(fd);
}

void modfd(int epollfd, int fd, int ev)
{
    epoll_event event;
    event.data.fd = fd;
    event.events = ev | EPOLLET | EPOLLONESHOT | EPOLLRDHUP;
    epoll_ctl(epollfd, EPOLL_CTL_MOD, fd, &event);
}

int http_conn::m_user_count = 0;
int http_conn::m_epollfd = -1;

void http_conn::close_conn(bool real_close)
{
    if((real_close==true) && (m_sockfd!=-1))
    {
        removefd(m_epollfd, m_sockfd);
        m_sockfd = -1;
        --m_user_count;//关闭一个连接时，将客户总量减1
    }
}

void http_conn::init(int sockfd, const sockaddr_in & addr)
{
    m_sockfd = sockfd;
    m_address = addr;

    //如下两行是为了避免TIME_WAIT状态，仅用于调试，实际使用应该去掉
    int reuse = 1;
    setsockopt(m_sockfd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));
    addfd(m_epollfd, sockfd, true);
    ++m_user_count;

    init();
}

void http_conn::init()
{
    m_check_state = CHECK_STATE_REQUESTLINE;
    m_linger = false;

    m_method = GET;
    m_url = nullptr;
    m_version = nullptr;
    m_content_length = 0;
    m_checked_idx = 0;
    m_read_idx = 0;
    m_write_idx = 0;
    memset(m_read_buf, '\0', READ_BUFFER_SIZE);
    memset(m_write_buf, '\0', WRITE_BUFFER_SIZE);
    memset(m_real_file, '\0', FILENAME_LEN);
}

//从状态机（参考8.6节）
http_conn::LINE_STATUS http_conn::parse_line()
{
    char temp;
    for(; m_checked_idx<m_read_idx; ++m_checked_idx)
    {
        temp = m_read_buf[m_checked_idx];
        if(temp=='\r')
        {
            if((m_checked_idx + 1) == m_read_idx)
            {
                return LINE_OPEN;
            }
            else if(m_read_buf[m_checked_idx + 1] == '\n')
            {
                m_read_buf[m_checked_idx++] = '\0';
                m_read_buf[m_checked_idx++] = '\0';
                return LINE_OK;
            }

            return LINE_BAD;
        }
        else if(temp == '\n')
        {
            if((m_checked_idx > 1) && (m_read_buf[m_checked_idx - 1] == '\r'))
            {
                m_read_buf[m_checked_idx-1]='\0';
                m_read_buf[m_checked_idx++]='\0';
                return LINE_OK;
            }

            return LINE_BAD;
        }
    }

    return LINE_OPEN;
}

//循环读取客户数据，直到无数据可读或者对方关闭连接
bool http_conn::read()
{
    if(m_read_idx >= READ_BUFFER_SIZE)
    {
        return false;
    }

    int bytes_read = 0;
    while(true)
    {
        bytes_read = recv(m_sockfd, m_read_buf+m_read_idx, READ_BUFFER_SIZE-m_read_idx, 0);
        if(bytes_read == -1)
        {
            if(errno == EAGAIN || errno == EWOULDBLOCK)
            {
                break;
            }
            return false;
        }
        else if(bytes_read == 0)
        {
            return false;
        }
        
        m_read_idx += bytes_read;
    }
    return true;
}

//解析HTTP请求行，获得请求方法，目标URL，已经HTTP版本号
http_conn::HTTP_CODE http_conn::parse_request_line(char * text)
{
    m_url = strpbrk(text, " \t");
    if(m_url == nullptr)
    {
        return BAD_REQUEST;
    }
    *m_url++ = '\0';

    char * method = text;
    if(strcasecmp(method, "GET") == 0)
    {
        m_method = GET;
    }
    else
    {
        return BAD_REQUEST;
    }

    m_url += strspn(m_url, " \t");
    m_version = strpbrk(m_url, " \t");
    if(m_version == nullptr)
    {
        return BAD_REQUEST;
    }
    *m_version++ = '\0';
    m_version += strspn(m_version, " \t");
    if(strcasecmp(m_version, "HTTP/1.1") != 0)
    {
        return BAD_REQUEST;
    }
    if(strncasecmp(m_version, "http://", 7) == 0)
    {
        m_url += 7;
        m_url = strchr(m_url, '/');
    }

    if(m_url==0 || m_url[0]!='/')
    {
        return BAD_REQUEST;
    }

    m_check_state = CHECK_STATE_HEADER;
    return NO_REQUEST;
}

//解析HTTP请求的一个头部信息
http_conn::HTTP_CODE http_conn::parse_headers(char * text)
{
    //遇到空行，表示头部子段解析完毕
    if(text[0] == '\0')
    {
        //如果HTTP请求有消息体，则还需要读取m_content_length字节的消息体，状态机转移到CHECK_STATE_CONTENT状态
        if(m_content_length != 0)
        {
            m_check_state = CHECK_STATE_CONTENT;
            return NO_REQUEST;
        }

        //否则说明已经得到一个完整HTTP请求
        return GET_REQUEST;
    }
    //处理Connection头部字段
    else if(strncasecmp(text, "Connection:", 11) == 0)
    {
        text += 11;
        text += strspn(text, " \t");
        if(strcasecmp(text, "keep-alive") == 0)
        {
            m_linger = true;
        }
    }
    //处理Content-Length头部字段
    else if(strncasecmp(text, "Content-Length", 15) == 0)
    {
        text += 15;
        text += strspn(text, " \t");
        m_content_length = atol(text);
    }
    //处理Host头部字段
    else if(strncasecmp(text, "Host:", 5) == 0)
    {
        text += 5;
        text += strspn(text, " \t");
        m_host = text;
    }
    else
    {
        printf("oop! unknow header %s\n", text);
    }

    return NO_REQUEST;
}

//此程序没有真正解析HTTP请求的消息体，只是判定它是否被完整读入
http_conn::HTTP_CODE http_conn::parse_content(char * text)
{
    if(m_read_idx >= (m_content_length + m_checked_idx))
    {
        text[m_content_length] = '\0';
        return GET_REQUEST;
    }

    return NO_REQUEST;
}

//主状态机（8.6章）
http_conn::HTTP_CODE http_conn::process_read()
{
    LINE_STATUS line_status = LINE_OK;
    HTTP_CODE ret = NO_REQUEST;
    char * text = nullptr;

    while(((m_check_state == CHECK_STATE_CONTENT) && (line_status == LINE_OK)) || ((line_status == parse_line())) == LINE_OK)
    {
        text = get_line();
        m_start_line = m_checked_idx;
        printf("got 1 http line: %s\n", text);

        switch(m_check_state)
        {
            case CHECK_STATE_REQUESTLINE:
            {
                ret = parse_request_line(text);
                if(ret == BAD_REQUEST)
                {
                    return BAD_REQUEST;
                }
                break;
            }
            case CHECK_STATE_HEADER:
            {
                ret = parse_headers(text);
                if(ret == BAD_REQUEST)
                {
                    return BAD_REQUEST;
                }
                else if(ret == GET_REQUEST)
                {
                    return do_request();
                }
                break;
            }
            case CHECK_STATE_CONTENT:
            {
                ret = parse_content(text);
                if(ret == GET_REQUEST)
                {
                    return do_request();
                }
                line_status = LINE_OPEN;
                break;
            }
            default:
            {
                return INTERNAL_ERROR;
            }
        }
    }

    return NO_REQUEST;
}

//当得到一个完整、正确的HTTP请求，分析目标文件属性。如果目标文件存在、对所有用户可读，且不是目录，则使用mmap将其映射到内存地址m_file_address处，并告诉调用者获取文件成功
http_conn::HTTP_CODE http_conn::do_request()
{
    strcpy(m_real_file, doc_root);
    int len = strlen(doc_root);
    strncpy(m_real_file + len, m_url, FILENAME_LEN - len -1);
    if(stat(m_real_file, &m_file_stat) < 0)
    {
        return NO_RESOURCE;
    }

    if(!(m_file_stat.st_mode & S_IROTH))
    {
        return FORBIDDEN_REQUEST;
    }

    if(S_ISDIR(m_file_stat.st_mode))
    {
        return BAD_REQUEST;
    }

    int fd = open(m_real_file, O_RDONLY);
    m_file_address = (char *)mmap(0, m_file_stat.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    close(fd);
    return FILE_REQUEST;
}

//对内存映射区执行munmap操作
void http_conn::unmap()
{
    if(m_file_address != nullptr)
    {
        munmap(m_file_address, m_file_stat.st_size);
        m_file_address = nullptr;
    }
}

//写HTTP响应
bool http_conn::write()
{
    int temp = 0;
    int bytes_have_send = 0;
    int bytes_to_send = m_write_idx;
    if(bytes_to_send == 0)
    {
        modfd(m_epollfd, m_sockfd, EPOLLIN);
        init();
        return true;
    }

    while(true)
    {
        temp = writev(m_sockfd, m_iv, m_iv_count);
        if(temp <= -1)
        {
            //如果TCP写缓冲没有空间，则等待下一轮EPOLLOUT事件。虽然在此期间，服务器无法立刻接收同一客户的下一个请求，但这可以保证连接的完整性
            if(errno == EAGAIN)
            {
                modfd(m_epollfd, m_sockfd, EPOLLOUT);
                return true;
            }
            unmap();
            return false;
        }

        bytes_to_send -= temp;
        bytes_have_send += temp;
        if(bytes_to_send <= bytes_have_send)
        {
            //发送HTTP相应成功，根据HTTP请求中的Connection字段决定是否立即关闭连接
            unmap();
            if(m_linger == true)
            {
                init();
                modfd(m_epollfd, m_sockfd, EPOLLIN);
                return true;
            }
            else
            {
                modfd(m_epollfd, m_sockfd, EPOLLIN);
                return false;
            }
        }
    }
}

//往写缓冲中写入待发送的数据
bool http_conn::add_response(const char * format, ...)
{
    if(m_write_idx >= WRITE_BUFFER_SIZE)
    {
        return false;
    }
    va_list arg_list;
    va_start(arg_list, format);
    int len = vsnprintf(m_write_buf + m_write_idx, WRITE_BUFFER_SIZE - 1 - m_write_idx, format, arg_list);
    if(len >= (WRITE_BUFFER_SIZE - 1 - m_write_idx))
    {
        return false;
    }
    m_write_idx += len;
    va_end(arg_list);
    return true;
}

bool http_conn::add_status_line(int status, const char * title)
{
    return add_response("%s %d %s\n", "HTTP/1.1", status, title);
}

bool http_conn::add_headers(int content_len)
{
    if(add_content_length(content_len)==false || add_linger()==false || add_blank_line()==false)
        return false;
    return true;
}

bool http_conn::add_content_length(int content_len)
{
    return add_response("Content-Length: %d\r\n", content_len);
}

bool http_conn::add_linger()
{
    return add_response("Connection: %s\r\n", (m_linger == true)?"keep-alive":"close");
}

bool http_conn::add_blank_line()
{
    return add_response("%s", "\r\n");
}

bool http_conn::add_content(const char * content)
{
    return add_response("%s", content);
}

//根据服务器处理HTTP请求的结果，决定返回给客户端的内容
bool http_conn::process_write(HTTP_CODE ret)
{
    switch(ret)
    {
        case INTERNAL_ERROR:
        {
            add_status_line(500, error_500_title);
            add_headers(strlen(error_500_form));
            if(false == add_content(error_500_form))
            {
                return false;
            }
            break;
        }
        case BAD_REQUEST:
        {
            add_status_line(400, error_400_title);
            add_headers(strlen(error_400_form));
            if(false == add_content(error_400_form))
            {
                return false;
            }
            break;
        }
        case NO_RESOURCE:
        {
            add_status_line(404, error_404_title);
            add_headers(strlen(error_404_form));
            if(false == add_content(error_404_form))
            {
                return false;
            }
            break;
        }
        case FORBIDDEN_REQUEST:
        {
            add_status_line(403, error_403_title);
            add_headers(strlen(error_403_form));
            if(false == add_content(error_403_form))
            {
                return false;
            }
            break;
        }
        case FILE_REQUEST:
        {
            add_status_line(200, ok_200_title);
            if(m_file_stat.st_size != 0)
            {
                add_headers(m_file_stat.st_size);
                m_iv[0].iov_base = m_write_buf;
                m_iv[0].iov_len = m_write_idx;
                m_iv[1].iov_base = m_file_address;
                m_iv[1].iov_len = m_file_stat.st_size;
                m_iv_count = 2;
                return true;
            }
            else
            {
                const char * ok_string = "<html><body></body></html>";
                add_headers(strlen(ok_string));
                if(false == add_content(ok_string))
                {
                    return false;
                }
            }
        }
        default:
        {
            return false;
        }
    }

    m_iv[0].iov_base = m_write_buf;
    m_iv[0].iov_len = m_write_idx;
    m_iv_count = 1;
    return true;
}

//由线程池中的工作线程调用，这是处理HTTP请求的入口函数
void http_conn::process()
{
    HTTP_CODE read_ret = process_read();
    if(read_ret == NO_REQUEST)
    {
        modfd(m_epollfd, m_sockfd, EPOLLIN);
        return;
    }

    bool write_ret = process_write(read_ret);
    if(false == write_ret)
    {
        close_conn();
    }

    modfd(m_epollfd, m_sockfd, EPOLLOUT);
}